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Charging battery pack with Xiaoxiang app

MrMatt

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Feb 26, 2021
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89
Hi,
have 4 Eve 3.2V cells, 280 amp hours.
And an Overkill BMS

Over the winter battery pack went low, so am now charging the pack

I am charging with a 45 amp charger, the clamps being on the main positive and negative cable from the battery pack.
Do I have to constantly visually monitor the voltage of the cells via the app, or will the BMS shut the charging down to each cell when the cell target Volts is reached?

I would think the BMS could not stop the charge by this "pathway" but BMS could stop an over charge from my solar cells for instance..

Thanks for your input
 
Hi,
have 4 Eve 3.2V cells, 280 amp hours.
And an Overkill BMS

Over the winter battery pack went low, so am now charging the pack

I am charging with a 45 amp charger, the clamps being on the main positive and negative cable from the battery pack.
Do I have to constantly visually monitor the voltage of the cells via the app, or will the BMS shut the charging down to each cell when the cell target Volts is reached?

I would think the BMS could not stop the charge by this "pathway" but BMS could stop an over charge from my solar cells for instance..

Thanks for your input
When the highest cell reaches the voltage you have set for high voltage cutoff .... charging will be disabled to ALL cells ..... there is no mechanism for doing this cell by cell.

It is best to also make sure the charge voltage is not excessive.
 
OK, thanks surprised the BMS can do this through the battery's main cables..
Yes, the charger is 45 ams, the280 amp eve batteries max charge rate is 1c

OR, I wonder if there is a max amp the BMS can handle. If the bms stops the charging to the batteries, where do all the 45 amps then go? To the BMS? - i guess?
 
I have to see if the Overkill BMS can handle dissipating 45 amps if it stops the batteries from further charge. Hopefully the spec for that is out there somewhere..
 
I have to see if the Overkill BMS can handle dissipating 45 amps if it stops the batteries from further charge. Hopefully the spec for that is out there somewhere..
The BMS acts like a switch in this case and no current will flow.
 
I have to see if the Overkill BMS can handle dissipating 45 amps if it stops the batteries from further charge. Hopefully the spec for that is out there somewhere..
As MrMatt mentioned, it shuts off charge current .... it will not have to dissipate the charge. I was wondering more about the voltage of the charger than the current.
 
I have to see if the Overkill BMS can handle dissipating 45 amps if it stops the batteries from further charge. Hopefully the spec for that is out there somewhere..
The solar panels don't push power to the SCC.
The SCC draws power from the solar panels.
If the BMS shuts down. The SCC will just stop drawing from the panels.
 
Thanks to all.
My solar panels were disconnected.
Ok I get it now ( been a while since I thought of this stuff) when the batteries reach their upper limit via BMS, the BMS switches the circuit to be open, so no more current can flow from the 45 amp charger.

Voltage: good question.. sad to say I had to look it up. It is 14.6 Volts. Would this be an issue vs 13.5Volts 45 amp charger.
Thank you for this question...
 
when the batteries reach their upper limit via BMS, the BMS switches the circuit to be open, so no more current can flow from the 45 amp charger.
You shouldn’t be controlling your charging with a BMS, that is the job of the charge controller. The BMS is a safety switch and does an abrupt power cut that is generally not good for your system.
This is especially true when your BMS cuts off the battery from the charge controller while it is powered by solar. Most SCC makers strongly recommend against disconnecting battery with solar energized.
 
Adjusting the SCC settings (switch to float) such that the BMS will never cut off unless there is serious issues with a cell seems to be the best plan.

Charging till each cell hits 3.5v will get you in a safe range and still have plenty of capacity. If the cells are well balanced, 14v is enough.
 
In my situation, the solar charge controller is disconnected from the batteries while I am charging the batteries from low SOC state - with the 45 amp charger..
Basically, - although the battery pack is in my bus, I guess I am doing a "bench charge" of the pack. The 2 accessories "hooked up" to the battery are turned off.

Right now, my cells are off a bit from each other, from the charger earlier today.
Cells being
3.356
3.359
3.361
3.358

Volts of the battery pack is 13.4
The cells in the past have always been extremely close to each other.



Will the cells self balance?, or will I have to charge each one individually, as in a top balance.

To tell you the truth, it is a little disconcerting for me as when I stopped the charge about 5 hours ago, the cells were in the 3.5 range, and now I see they dropped.

I am going to resume charging them - now with the SCC, once I hook the SCC up again to the battery pack.. But rain tomorrow, so will have to wait.

I really appreciate the comments, I definitely want to know the best way to do to maintain my batteries in the most healthy way. Please do correct me if my approach is wrong, I am wanting to learn.


Thank you all again for your instruction..
 
Good to know, thought I was past being a newbie, guess not.

Any thought about the voltage drop? is this normal? Possible the batteries have to "settle" or something like that after being charged for hours at 45 amps
 
Thanks, it is always good to see normal behavior......


ok, nice, will copy and print that for my "VW Solar" folder

Thank you
 
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